A vinyl chloride-based resin having excellent mechanical properties, processability and chemical resistance, and is inexpensive compared with other resins has been developed. This resin can therefore be used in a wide range of applications, but primarily in the field of housing as, for example, a pipe, a joint, a flat plate, a gutter, a sash, and siding. Polyvinyl chloride (PVC) is currently primarily used but has low heat resistance and is easily thermally deformed. PVC is hence limited in being used at a high temperature. Therefore, in order to improve the heat resistance of a vinyl chloride-based resin, a method for subjecting the vinyl chloride-based resin to after-chlorination is generally employed, and the resultant after-chlorinated vinyl chloride-based resin (hereinafter referred to as “chlorinated vinyl chloride-based resin”) can be used as a pipe for a fire extinguishing sprinkler and a pipe for hot water supply (see PTLs 1, 2 and 4).
A chlorinated vinyl chloride-based resin has an increase in brittleness of the resin and has lower impact strength because the chlorine content therein is increased. Therefore, in order to increase the impact strength for attaining balance in mechanical properties, it is necessary to add a larger amount of an impact absorber to the chlorinated vinyl chloride-based resin composition than that to a conventional PVC. As the impact absorber, a rubber-based impact absorber having a low glass transition temperature is used. The impact strength of a chlorinated vinyl chloride-based resin is improved in proportion to the ratio of the rubber-based impact absorber in a resin composition. However, if the ratio of the rubber-based impact absorber is excessively large, the heat resistance, that is, a feature of the chlorinated vinyl chloride-based resin, is largely degraded, and its processability is also lowered. Therefore, examinations are being made for various resin compositions sufficient in all of the aspects of heat resistance, mechanical properties, and processability (see PTLs 1 to 4).